The present invention relates in general to cannulas and in particular to an infiltration cannula that allows for intermittent infiltration of fluids, such as a local anesthetic.
Many medical procedures require infiltration of fluids, such as a local anesthetic. One method of infiltration of local anesthetic is via an infiltration cannula. Infiltrators currently on the market are known as sprinkler-tip or Klein (the present applicant) needle infiltrators. These cannulas are constructed out of a rigid stainless steel and have one or more apertures, which are typically round or oval, and are distributed about the distal end of the cannula. The apertures are distributed over about 15% to 25% or less than 5.0 cm. of the distal end of the cannula needle. These traditional infiltration cannulas are intended to be inserted through a small incision in the patient's skin and then moved in and out through the subcutaneous tissue while a dilute solution of local anesthetic (or other pharmaceutical solution) is ejected through the distal apertures. Such infiltrators typically have a blunt tip and require the placement of a small hole (made by a one mm skin-biopsy punch or a small surgical blade) through which the blunt tipped cannula can be passed. The piston-like in and out motion of the cannula causes the patient discomfort.
Another method of fluid insertion is via a peripherally inserted central catheter, also called a PICC line comprising an elongate plastic tube that is placed inside a vein of the patient. PICC lines are typically used for procedures requiring delivery of fluids over a prolonged period of time. For example, a PICC line may be used when a patient needs to receive intravenous (IV) fluids, such as medication or nutrients over a prolonged period of time, such as a week or more.
The On-Q® Pain Management System marketed by I-Flow® Corporation employs a PICC line type system for continuously providing local anesthetic. This system provides prolonged local anesthesia by means of an elastomer (elastic container) device that continuously infiltrates a solution of local anesthesia over many hours. The On-Q® device is a long soft flexible tube with many small holes arranged along a significant portion of the tube. The On-Q® device is designed to be positioned within a surgical wound at the time of surgery; after the surgical wound is closed the On-Q® device permits slow steady infiltration of a local anesthetic solution into the wound, thereby attenuating post-operative pain. The On-Q® device cannot be inserted through a tiny hole in the skin into subcutaneous tissue. Thus there is a need for a simple device that can permit the direct percutaneous insertion of a multi-holed infiltration cannula into subcutaneous tissue for the localized delivery of medications such as local anesthetics, chemotherapeutic agents, or crystalloids for parenteral hydration.
Traditional techniques for subcutaneous injection of local anesthetic solutions use a high-concentration/low-volume of local anesthetic. This is associated with a rapid systemic absorption of the local anesthetic. In order to achieve a prolonged local anesthetic effect, the traditional techniques for using local anesthetics necessitate either frequent repeated injections or slow continuous subcutaneous infusion of the local anesthetic. As described above, repeated injections or piston-like movement of the cannula causes patient discomfort. Slow continuous infiltration may not be desirable in certain situations. Furthermore, continuous infiltrations restrict patient movement for extended periods of time which also cause the patient discomfort. Thus, there is a need for a system for infiltration of a local anesthetic into subcutaneous tissue which decreases patient discomfort, and allows prolonged local anesthesia.